28 Fluid Power
a pump during the idle time of a press or other
machine. During peak operating time the charged
accumulator assisted the pump by supplying high
volumes of fluid needed for operation.
The hydraulic intensifier was used to more
easily obtain high system pressures for use in bail-
ing, metal forming, forging, or other applications.
The intensifier, which usually consisted of some
combination of large and small diameter rams,
used the area differences of the rams to boost sys-
tem pressure above the capability of the pump.
This principle allowed the use of higher pressure
even when the technology of the time did not allow
pumps to operate at extremely high pressure.
Pressurized water was extensively used to dis-
tribute power to businesses and manufacturers
in several cities in Great Britain. By 1900, it was
considered economical to transmit power up to
15 miles from a centralized pumping station. These
systems provided water under several hundred
pounds per square inch of pressure that could be
directly used for the operation of presses, hoists,
and water motors. These systems continued in use
until electrical generating and distribution sys-
tems were perfected.
Fluid power development and use during the
nineteenth century was very extensive. This use
involved the generation of power through the
design of effective water turbines; the transmis-
sion of power using central power stations and
elaborate distribution lines; and the use of fluid
power in construction, manufacturing, and mate-
rial distribution systems.
Recent history
The emphasis on the development of fluid
power applications decreased as the use of electric-
ity grew in the late 1800s and early 1900s. Devel-
opment concentrated more in the heavy industrial
and mobile areas where fluid power applications
appeared to be most practical. Generally, these fac-
tors have promoted progress in fluid power appli-
cations in recent years:
■ Development of new materials.
■ Miniaturization of components.
■ Effective electrical/electronic control.
Improvements were made in sealing devices
and machining techniques that reduced both
internal and external leaks. This, in turn, improved
system efficiency. Reducing external leaks also
allowed use in applications where cleanliness was
an important factor. Water was replaced in hydrau-
lic systems by petroleum-based fluids, which
improved lubrication and eliminated the danger
of freezing in cold climates.
Military applications contributed to the devel-
opment of fluid power. A milestone occurred in
1906 when hydraulic systems first appeared on
a warship, the battleship USS Virginia. These
hydraulic systems replaced many mechanical and
electrical systems. Since that time, all branches
of the military have incorporated fluid power
on numerous devices to solve problems in gun-
nery, materials handling, navigation, and support
services.
The development and refinement of the con-
cept of compact hydraulic units in the 1920s had
a far-reaching effect, extending to today’s fluid
power applications, Figure 1-19. These self-con-
tained systems include the power source, pump,
and reservoir. The units have been applied to a
full range of industrial and consumer applications.
Central hydraulic and pneumatic power systems
have remained in large industrial applications, but
the more-compact direct system adds flexibility.
Figure 1-18. Modern sealing devices are often taken
for granted. However, their development in the late
1700s by Bramah and Maudslay was instrumental
to the practical application of fl uid power principles.
(Photo courtesy of Apple Rubber Products, Inc.)